1. Technical Field
The present invention relates to a method and apparatus for data transmission in general, and in particular to a method and apparatus for transmitting data on a bus. Still more particularly, the present invention relates to a method and apparatus for transmitting data on a bus connected either as separately packaged chips or as separate areas within a chip.
2. Description of the Prior Art
The technique of using a group of wires typically known as a bus to transmit data has been in common use since the early days of electronic computers. There are many advantages in using a single interconnecting scheme such as a bus for a computer system. For example, various subsystems within a computer system can be interfaced with each other via a bus. In addition, new devices and peripherals can easily be added or even be ported between computer systems that use a common bus. Furthermore, because a single set of wires can be shared among multiple sources and destinations, the cost associated with a bus implementation is relatively low.
However, for computer systems that are specifically designed for business applications, where the demands on input and output are relatively high, it is a major challenge to design a bus system capable of meeting these demands in an efficient manner. With conventional design, data is generally driven on to a bus, using logic voltage levels to encode and transmit a data bit in every wire within the bus, and this method of data transmission is sufficient for relatively narrow buses. But when wider buses are needed to meet the ever increasing throughput requirements, the problem of capacitive and inductive coupling between adjacent parallel bus wires and simultaneous switching of a large number of drivers with consequent peak current demand, becomes more significant. This is especially true for bus wiring within a chip as capacitive and resistive effects are much larger in such an environment due to the small dimensions of the bus wires and the close proximity of wire spacings from adjacent conductors. The present disclosure provides an improved method and apparatus for transmitting data on a bus such that these problems can be greatly reduced.